Air cushion device



vMay 23, 1967 H. A. MACKiE ETAL 3,321,038

AIR CUSHION DEVICE Original Filed Jan. 25, 1960 2 Sheets-Sheet 1INVENTORS 2641 G1 77/2209? & mffoer/%% ryzer ATTORNEY y 23, 1967 H. A.MACKIE ETAL. 3,321,038

AIR CUSHION DEVICE Original Filed Jan. 25, 1960 2Sheets-Sheet 2 ATTORNEYUnited States Patent C ice 3,321,038 AIR CUSHION DEVICE Harry A. Mackieand Robert W. Veryzer, both of Birmingham, Mich, assignors to GeneralMotors Corporation, Detroit, Mich, a corporation of DelawareContinuation of application Ser. No. 4,465, Jan. 25, 1960.

This application Jan. 19, 1966, Ser. No. 526,943

5 Claims. (Ci. 180-4) This application is a continuation of abandonedapplication Ser. No. 4,465, filed Jan. 25, 1960, in the names of Harry.A. Mackie and Robert W. Veryzer, entitled, Air Cushion Device, andassigned to the assignee of the present invention.

This invent-ion relates to wheelless load supporting devices and moreparticularly to vehicles which are supported relative to the groundsolely by means of a low pressure free air cushion.

Very recently, considerable effort has been directed toward developingpractical wheclless passenger and cargo carrying vehicles which utilizethe so-called ground cushion phenomenon as the sole means for supportingthe vehicle relative to the ground. Among the various known forms ofload supporting devices which are considered within the meaning of theterm ground cushion are low pressure air bearings and plenum chambers.In the former, a platform having a fiat lower surface is provided with acentral aperture through which air is introduced from a low pressurehigh volume source. This air radiates outwardly from the aperturebetween the lower surface of the platform and the supporting surfaceforming a thin layer of air lubricant which supports the platform in thefrictionless spaced relation from the supporting surface. In the latter,the platform is inverted cup shape in form providing a permanent cavityfacing the supporting surface. Air in introduced in the same manner asthe air bearing but forms a relatively large volume cushion within thecavity rather than the thin layer characteristic of the air bearing.While both of the foregoing have certain fundamental characteristics incommon, air bearings differ significantly from plenum chambers in thatthe former operate most efliciently when clearance between the lowersurface of the vehicle and the ground is on the order of 5 tothousandths of an inch. By contrast, vehicles utilizing a plenum chambernormally function at an elevation above the ground approximately 5% ofthe diameter of the plenum chamber.

Although the low pressure air bearing is extremely simple structually,it exhibits very low tolerance to load unbalance. In addition, the veryshallow clearance or spacing between the ground and supported platformchar acteristic of this form severely limits the possibility ofpractical application thereof since any vehicle so supported would beunable to negotiate even moderate irregularities on the surface overwhich it was intended to travel.

Plenum chambers on the other hand possess greater capability in clearingsurface obstacles due to their higher normal operating clearance.However, in common with the low pressure air bearing, the plenum chamberexhibits a marked tendency to ground out if subjected to moderate loadunbalance. It has already been proposed to improve the obstacle clearingability of plenum chambers by providing such vehicles with a dependingflexible peripheral skirt which would yieldably deflect when an obstaclewas encountered. While this expedient achieves some success insofar asobstacle clearing is concerned, it accomplishes little if anything interms of improved stability under conditions of unbalanced load.

An object of the present invention is to provide an air cushionsupported vehicle which is capable of surmounting substantialirregularities on the surface over which it Patented May 23, 1961travels while providing a high degree of tolerance to load unbalance.

Another object is to provide an air cushion supported vehicle wherein asubstantially flat platform has disposed thereunder and secured to theperimeter thereof a flexible diaphragm having a central aperture, thediaphragm and platform forming an annular cavity which is subjected toair pressure of the same level as the air pressure forming the aircushion between the vehicle and the ground.

A further object is to provide an air cushion supported vehicle having afiat platform and a downwardly bulged flexible undersurface forming apressurized cavity, the undersurface being capable of deflectivelyenveloping road surface obstacles without causing an increase inpressure in the pressurized cavity.

A still further object is to provide a device of the stated characterwherein the central aperture in the diaphragm is capable of adjustablepositioning in any of a plurality of vertical positions above thelowermost exremity of the diaphragm when the latter is inflated so as toprovide a plenum cavity of generally frusto-conical shape between thelower surface of the diaphragm and the adjacent ground which is occupiedby low pressure air acting to support both the platform and diaphragmabove the ground at a vertical level providing moderate clearancebetween the ground and the lowermost extremity of the diaphragm.

Yet another object is to provide a device of the stated character inwhich the profile of the flexible undersurface automatically changes so:as to shift the location of the plenum cavity horizontally in adirection counteracting the unbalanced load applied to the platform.

These and other objects, advantages, and features of the invention willbecome more fully apparent as reference is had to the accompanyingspecification and draw ings wherein:

FIGURE 1 is a perspective view of a materials handling vehicle utilizingthe present invention;

FIGURE 2 is a diagrammatic view illustrating the form and arrangement ofa load supporting device according to the invention;

FIGURES 3, 4, 5 and 6 are views similar to FIGURE 2 illustratingfunctional characteristics of the device under various conditions ofoperation; and

FIGURE 7 is a modified form of the invention shown in FIGURE 2.

Referring now to the drawings and particularly FIG- URE 2, there isshown a load supporting device in which the reference numeral 2designates a thin rigid flat platform having a central opening 4 formedtherein. Disposed over opening 4 and secured to the upper surface ofplatform 2. is a low pressure high volume air source, which in theillustrated embodiment, takes the form of a centrifugal blower 6, havinga discharge end 8 which is axially aligned with opening 4. Blower 6 maybe driven by any suitable source of power such as a gasoline engine,

battery powered electric motor, or the like. It will be understood thatthe invention is not limited to the particular type of blower shown, anyother known form of loW pressure high volume air delivery being equallysuitable and within the contemplation of the invention.

The structure thus far described is already well known in the art as alow pressure air bearing which, when blower 6 is operated, rises abovethe ground 10' a few thousandths of an inch so that a constantly movingthin layer of air lubrication exists between the lower surface of theplatform and the ground. It is also known that the structure thus fardescribed exhibits the ability to support extremely heavy loads in termsof power expended while maintaining the platform in frictionless spacedrelation from the ground. However, in heretofore known forms, airbearing platforms have required an exceedingly smooth surface upon whichto operate, owing to the extremely shallow clearance. In addition, suchdevices functioned properly only if the supported load was verycarefully balanced with reference to the center of gravity of theplatform.

To overcome the foregoing shortcomings in accordance with the presentinvention, platform 2 has disposed thereunder a preformed flexiblediaphragm element 12, the outer periphery or margin 14 of which issecured in air tight engagement with the perimeter 16 of the platform.As seen best in FIGURE 2, the preformed shape of diaphragm element 12 issuch that the cross-sectional dimension of the essentially horizontallyextending portion thereof disposed in juxtaposed relation to supportsurface is at least three times that of the essentially verticallyextending portion disposed in radially confronting relation toatmosphere. Although shown relatively thick for clarity, diaphragm 12 ispreferably formed of a thin, tough, stretch resistant material such asthe polyester reaction product of terephthalic acid and ethylene glycolknown as Mylar. Centrally thereof, diaphragm 12 is formed with acircular throat or aperture 18 which is axially aligned with aperture 4in platform 2. Aperture 18 is preferably bounded by a bead having ametal ring 22 embedded therein. Ring 22 is attached to one end of aflexible cable 24, the other end of which in turn is connected to arotatable control rod 26 mounted in blower 6. By manipulation of a knob28, cable 24 winds and unwinds on rod 26, thereby permitting selectionof various vertical operat ing levels of ring 22 relative to platform 2(FIGURE 3).

Operation of the structure shown in FIGURE 2 is as follows: (it will beunderstood that prior to operation of blower 6, diaphragm 12 will be ina collapsed condition between platform 12 and the supporting surface10). Upon energization of blower 6, air enters the inlet thereof (notshown) and is compressed to a suitable pressure, e.g,. 11 lbs. persquare foot, and ejected from the discharge end 8 through opening 4 tothe undersurface of platform 2. From opening 4, air enters the initiallycollapsed cavity 30 formed between the undersurface of the platform andthe top surface of the diaphragm. Because of the attachment of margin 14of the diaphragm at ,the perimeter of the platform, the pressurized airthus introduced cannot escape from cavity 36 except through throat 18,which is occupied by continuously flowing air at the same pressure,hence the diaphragm will initially inflate and lift the platformvertically. After sufficient pressurized air has entered cavity 30 toinflate the diaphragm and support the platform, further discharge ofpressurized air from blower 6 is required to pass through throat 18 intothe frusto-conical cavity 32 created between the underside orhorizontally extending portion of the diaphragm and the supportingsurface 10 as a result of inflation of cavity 30. The pressurized airthus introduced into cavity 32 thereafter functions to provide an aircushion supporting the diaphragm and the platform in frictionlessrelation to the supporting surface in essentially the same manner asaccompained by a conventional plenum chamber. It will be noted thatduring operation the diaphragm 12 assumes an annular convolution orconfiguration defining a narrow annular zone of circular clearance 34relative to support surface 10 at the outer extremity of plenum cavity32 which is relatively shallow in vertical extent. This narrow annularzone of shallow clearance functions to meter or throttle the rate ofescape of air from plenum cavity 32 so as to maintain pressurized airtherein equal to the delivery rate of blower 6. Since the pressure incavity 30 is substantially equal to the pressure in cavity 32, anegligible pressure differential exists therebetween while a substantialpressure differential exists between cavity 30 and atmospheric pressureradially outwardly of the narrow annular zone of clearance 34.Therefore, the vertically extending portion of the diaphragm betweenclearance 34 and outer margin 14 defines a continuously curvingcross-section or radius, while, as previously stated, the underside orhorizontally extending portion of the diaphragm defines a generallyconical cross-section. Uniformity of the vertical extent of clearance 34is constantly maintained by automatic change in the profileconfiguration of the diaphragm due to pressure exerted on the inner wallthereof by pressurized air in cavity 30. As a result, should the devicebe negotiating an undulating surface such as shown in FIGURE 4, thediaphragm similarly automatically adjusts to the adjacent surfaceundulation and maintains the uniform circular clearance 34.

Because pressurized air in cavity 30 automatically adjusts the diaphragmprofile so that its lowest extremity maintains uniform clearance withsupporting surface, a device according to the invention possesses theability to continue functioning efiiciently even though a load isimposed thereon which substantially unbalances the center of gravity ofthe vehicle. As illustrated in FIG- URE 5, if load is distributedunevenly as in the form of heavy weight 36 on the left and a lightweight 38 on the right, platform 2 will tilt downwardly on the sidesupporting the heavier weight. However, the portion of diaphragm 12located on the more heavily Weighted side assumes a profile orcross-sectional configuration wherein the vertically extending portionbetween clearance 34 and outer periphery 14 forms a small radius 40while the lightly weighted side rises allowing the vertically extendingportion of the diaphragm at that side to assume a profile configurationof much larger radius 42. Naturally, cross-sectional radii taken alongthe circumference of the diaphragm between radius 40 and radius 42 willvary progressively between the two extremes. As will be evident from thedrawing, the result of the differing radii is that the clearance 34 isstill maintained uniformly vertically, but the lateral position of thecircle defined by clearance 34 is shifted in the direction of the moreheavily weighted side. Thus, in effect, the air cushion support areaautomatically adjusts itself horizontally to achieve realignment withthe modified center of gravity of the vehicle together with itsmaldistributed weight. As an adjunct further assisting the horizontaltranslation of the air cushion, it will be seen that cable 24 suspendingring 22 is free to swing laterally and thus allow limited lateralphysical displacement of the central portion of the diaphragm 12relative to platform 2.

FIGURE -6 illustrates schematically the behavior of the diaphragm whenthe vehicle encounters a localized projection or irregularity which isto be progressively traversed by the vehicle. In such case, a localizedarea 43 of the diaphragm deflects upwardly to maintain a verticalclearance substantially equal to the continuous circular clearance 34normally present. It is to be particularly noted that upward bulging ordeflection of a localized portion of the diaphragm does not increase thelevel of pressure in cavity 30, since the volume of air so displaced isfree to exit through throat 18. Lack of resistance to localized upwarddeflection of diaphragm 12 is further explained by the fact that thepressure level in cavity 30 and plenum cavity 32 are substantiallyequal. Because of the ready displacement of air from cavity 30 uponencountering a localized obstacle, the vehicle negotiates such obstacleswithout perceptible bounce.

In FIGURE 7, there is illustrated a modified form of the invention inwhich the platform 2 is provided with a plurality of openings 44 whichallow admission of air from blower 6 directly into the cavity 30radially outboard of throat 18 and thereby eliminate any possibility offailure of the diaphragm to inflate when the vehicle has been startedfrom a collapsed position. It is to be noted that the specific locationof openings 44 is not in any sense critical and may be even furtheroutboard as for example at the outermost extremity of the platformperimeter. Because of this extreme flexibility in location of thepressurized air inlet, the invention is extremely well adapted for usein devices such as the pallet type materials ,9 handling truck shown inFIGURE 1. In the form shown in FIGURE 1, the platform 46 is preferablyrectangular in form and a blower or compressor 48 and power supply 50are located at the extreme end thereof to provide a maximum ofunobstructed load supporting surface. Naturally, the diaphragm 52 willbe preformed to conform to the rectangular form of the platform.However, operationally, the truck shown in FIGURE 1 functions in thesame manner as described with respect to FIG- URES 2 and 7. Inasmuch asthe materials handling truck is devoid of any frictional contact withthe ground when in operation, propelling thereof from one locationthereof to another is virtually effortlessly accomplished manually bymeans of guide handles 54. It is to be understood, however, that theinvention is not in any sense limited to application requiring manualpropulsion, this form being shown for illustrative purposes only.

From the foregoing it will be seen that a novel and improved loadsupporting vehicle has been provided. It is to be particularly notedthat a structure according to the invention is unusually well suited foruse in the materials handling field since it is virtually effortlesslypropelled in a straight line in any direction from a given point. Hence,the complicated and expensive steering apparatus commonly required toprovide wheeled materials handling vehicles with sufficientmaneuverability is totally eliminated. In addition to the above, amaterials handling truck utilizing the present invention has theadditional advantage of offering an extremely low profile when not inoperation, thereby greatly reducing difiiculty in loading of materialsto be transferred.

While several embodiments of the invention have been shown anddescribed, it will be apparent that other changes, modifications, andapplications thereof may be made. It is, therefore, to be understoodthat it is not intended to limit the invention to the embodiments shown,but only by the scope of the claims which follow.

We claim:

1. A ground proximate air cushion device comprising, a platform, adiaphragm underlying said platform and fixed thereto at its outer andinner margins defining an annular depending convolution approachingcontact with the ground at a narrow annular zone between the margins,means for supplying air at superatmospheric pressure within theconvolution, means for establishing and maintaining correspondingpressure in the space between the diaphragm and the ground surfaceradially within the narrow annular zone and flowing with throttlingthrough the said zone whereby the diaphragm is subject to a firstsignificant pressure differential between supplied air pressure andatmospheric pressure radially outwardly of the zone and a secondnegligible pressure differential between supplied air pressure atopposite sides thereof radially inwardly of the zone, said firstpressure differential acting to induce a substantially circularcross-sectional curvature in said convolution from the outer margin tosaid narrow annular zone, and said first and second pressuredifferentials coacting to permit the former to radially tension theportion of said convolution within said zone into a substantiallyconical cross-section.

2. The structure set forth in claim 1 wherein the diaphragm centralportion is connected to said platform in a manner enabling limitedlateral movement relative to said platform.

3. The structure set forth in claim 1 wherein the projected apex of saidfrusto-conical section lies beneath the upper surface of said platform.

4. A ground proximity fluid cushion supporting device comprising, aplatform, a flexible diaphragm disposed horizontally beneath saidplatform, said diaphragm including a peripheral portion hermeticallyattached to said platform, an intermediate annular portion defining acontinuously curving depending convolution spaced from said platformprogressing from the perimeter to a narrow annular zone approachingcontact with the ground and a dished central portion connected centrallythereof to said platform above the lowermost extremity of saidconvolution thereby forming an inflatable annular cavity between saiddiaphragm and said platform and plenum cavity said diaphragm and theground, the latter cavity being bounded by a perimetrical throttling gapformed between the lowermost extremity of said convolution and theground, means for introducing fluid under pressure directly into one ofsaid cavities, and means for establishing and maintaining equal fluidpressure in said cavities, the cross-sectional radius of saidcontinuously curving convolution progressively decreasing when saidplatform descends in parallel relation to the ground and progressivelyincreasing when said platform ascends in parallel relation to theground.

5. The invention set forth in claim 4 wherein the crosssectional radiusvaries progressively around the circumference of said convolution froman increased to a decreased condition when said platform is inclinedrelative to the ground whereby said perimetrical throttling gap iscaused to shift laterally relative to said platform in the direction ofsaid decreased cross-sectional radius.

No references cited.

A. HARRY LEVY, Primary Examiner.

Edward M. Fletcher, Jr.

UNITED STATES PATENT OFFICE CERTIFICATE- OF CORRECTION Patent N00 3,321,038 May 23, 1967 Harry An Mackie e1: alp

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below Column 1, line 36, for "in", first occurrence, read iscolumn 3, line 58, for "accompained" read accomplished column 4, line14, after "with" insert the column 6, lines 28 and 29, for "and plenumcavity" read and a plenum cavity between "0 Signed and sealed this 28thday of November 19670 (SEAL) Attest:

EDWARD J. BRENNER Attesting Officer Commissioner of Patents

1. A GROUND PROXIMATE AIR CUSHION DEVICE COMPRISING, A PLATFORM, ADIAPHRAGM UNDERLYING SAID PLATFORM AND FIXED THERETO AT ITS OUTER ANDINNER MARGINS DEFINING AN ANNULAR DEPENDING CONVOLUTION APPROACHINGCONTACT WITH THE GROUND AT A NARROW ANNULAR ZONE BETWEEN THE MARGINS,MEANS FOR SUPPLYING AIR AT SUPERATMOSPHERIC PRESSURE WITHIN THECONVOLUTION, MEANS FOR ESTABLISHING AND MAINTAINING CORRESPONDINGPRESSURE IN THE SPACE BETWEEN THE DIAPHRAGM AND THE GROUND SURFACERADIALLY WITHIN THE NARROW ANNULAR ZONE AND FLOWING WITH THROTTLINGTHROUGH THE SAID ZONE WHEREBY THE DIAPHRAGM IS SUBJECT TO A FIRSTSIGNIFICANT PRESSURE DIFFERENTIAL BETWEEN SUPPLIED AIR PRESSURE ANDATMOSPHERIC PRESSURE RADIALLY OUTWARDLY OF THE ZONE AND A SECONDNEGLIGIBLE PRESSURE DIFFERENTIAL BETWEEN SUPPLIED AIR PRESSURE ATOPPOSITE SIDES THEREOF RADIALLY INWARDLY OF THE ZONE, SAID FIRSTPRESSURE DIFFERENTIAL ACTING TO INDUCE A SUBSTANTIALLY CIRCULARCROSS-SECTIONAL CURVATURE IN SAID CONVOLUTION FROM THE OUTER MARGIN TOSAID NARROW ANNULAR ZONE, AND SAID FIRST AND SECOND PRESSUREDIFFERENTIALS COACTING TO PERMIT THE FORMER TO RADIALLY TENSION THEPORTION OF SAID CONVOLUTION WITHIN SAID ZONE INTO A SUBSTANTIALLYCONICAL CROSS-SECTION.